Beach and shoreface grain size as also topography and morphodynamic state along part of the beach arc in the Rio das Ostras-cape Búzios embayment are strongly dominated by the deposition of fine sediments provenient from the Sao Joao river. Sandy sediments dominate the northern upper shoreface while the southern upper shoreface is covered by muddy sediments. Relict coarse to very coarse sands occurs at the middle to lower shoreface. Influence of river sediments become increasingly significant to beach and shoreface morphology from the middle of the beach arc in direction to the south. Northward of the Sao Joao river mouth the beach is coarse grained with a steep beach face, narrow beach berm and almost absence of a surf zone. Upper shoreface is also coarse grained and steep. Southward of the river mouth, in the direction of net suspended sediment transport, the beach becomes increasingly finer grained and the topographic profile gradually flattened as also the shoreface, with the beach stage changing to dissipative.